Field of the Invention
The present invention relates to an avalanche photodiode using a silicon nanowire and a silicon nanowire photomultiplier using the avalanche photodiode.
Description of the Related Art
A silicon photomultiplier (SiPM) has been proposed to replace a conventional photomultiplier tube (PMT). The silicon photomultiplier and the photomultiplier tube are devices for detecting single photon. A conventional silicon photomultiplier (SiPM) includes a plurality of micropixels. Each micropixel uses an avalanche photodiode (APD) for outputting a signal amplified by avalanche gain in response to photons incident thereon.
A nanowire device uses a nano-scale nanowire, and is applied to various fields, and research and development thereon for application in semiconductor fields is ongoing. In order to fabricate a nanowire device, it is important to manufacture a nanowire.
Methods of manufacturing a nanowire device are broadly classified into two depending on the type of approach, namely a “top-down” process, for directly manufacturing a nanowire device at a desired position by etching a material such as silicon using a conventional semiconductor process, especially ultrafine photolithography, and a “bottom-up” process for synthesizing nanowires using VLS (Vapor-Liquid Solid) growth and aligning them at a specific position to manufacture a nanowire device.
The VLS growth method is employed in nanowire growth for most semiconductors and metal materials, such as Si, ZnO, GaN, InP, and metals. However, the fabrication of a nanowire device requires the formation of an additional structure such as an electrode after the grown nanowires are aligned at a desired position.
The position at which the nanowires are to be aligned is controlled by the process of aligning nanowires at a desired position through any process, such as electrophoresis for nanowire device applications, or aligning nanowires through fluid flow using fluid channels.
However, even when such a process is used, it is very difficult to precisely control the position at which nanowires are located, and low yield may result even after the aligning process.
Furthermore, an additional electrode structure for the electrical connection of aligned nanowires is fabricated using an expensive e-beam lithography process.
The top-down method of manufacturing a nanowire device includes directly forming a nanowire by etching silicon. Since the formation of nanowires having a diameter of ones of nm requires an ultrafine pattern, an ultrafine patterning process such as e-beam lithography is adopted. Although nanowires may be formed to a desired size at a desired position through such a top-down process, expensive equipment, such as an e-beam lithographer is required, and the production rate is low. Moreover, the nanowires obtained thus are non-uniform compared to nanowires obtained by self-alignment, and the nanowires have to be fabricated on an insulator in order to function as an electric device.